1. Field of the Invention
The present invention relates to an electronic endoscope apparatus which alternately repeats obtainment of a partial image signal using a part of a light receiving area of an imaging element and obtainment of a partial image signal using the remaining part of the light receiving area, and which obtains an image signal corresponding to an image of an observation object using a partial image signal obtained in the n-th obtainment and a partial image signal obtained in the (n+1)th obtainment.
2. Description of the Related Art
Conventionally, various kinds of electronic endoscope apparatus which obtain color image signals by taking photographs of an image of an observation object by scope units which have imaging elements, and which display color images based on obtained color image signals have been proposed.
As the electronic endoscope apparatus described above, an electronic endoscope apparatus which obtains an image signal, for example, using a color filter, such as a complementary color filter, according to a chrominance line-sequential method has been proposed (please refer to Japanese Unexamined Patent Publication No. 11 (1999)-136693).
In the electronic endoscope apparatus according to the chrominance line-sequential method, signal electric charges of two adjacent pixels with respect to the vertical direction are added and read out. When the signal electric charges are added, signal electric charges of a different pair of adjacent pixels are added in an odd field and in an even field. Then, a whole image signal which represents a whole image is obtained using a partial image signal which is read out from the odd field and a partial image signal which is read out from the even field.
However, when, for example, a stomach or the like in a body cavity is photographed using an electronic endoscope apparatus according to the chrominance line-sequential method as described above, if the direction of the leading edge of a scope unit of the electronic endoscope apparatus is quickly changed from the stomach wall to the center of the stomach, the luminance of an image signal obtained in the odd field and that of an image signal obtained in the even field may be completely different from each other. In that case, a striped pattern is formed in a displayed image, and a so-called flicker is generated.